"The Green Bay Packers took a chance by keeping just two running backs on the roster to start the season, and after one game have lost the most important one for the entire year.

Starter Ryan Grant was injured in the second quarter of the Packers' 27-20 victory over Philadelphia Sunday when safety Quintin Mikell pulled him down from behind and landed with his full weight on Grant's right ankle.

According to an NFL source, Grant tore the ligament that holds the two ankle bones together and will require surgery to insert screws to hold it in place. Grant also suffered a slight fracture of the upper fibula, but it is a minor injury and will heal on its own.

Grant said on his Twitter account that he probably would have been able to return later this year, but that the Packers decided they couldn't afford to hold his spot that long.

"I would miss too many weeks and put the team in a bind roster-wise," he tweeted.

The Packers filled Grant's roster spot by signing Dimitri Nance, a 5-foot-10, 219-pound rookie, off Atlanta's practice squad. Practice squad players can be signed off any team as long as they are placed on the 53-man roster.

With Grant gone, the Packers will head into the first game at Lambeau Field this Sunday with Brandon Jackson in Grant's starting position and fullback John Kuhn and Nance backing him up.

General manager Ted Thompson rolled the dice by cutting running back Kregg Lumpkin and keeping just two halfbacks to start the season. Others thought so highly of Lumpkin that four teams put in claims on him and he was awarded to the Tampa Bay Buccaneers.

The fact Grant had never missed a game because of injury through 782 carries over three seasons probably influenced Thompson's decision. Whether Jackson can match the 1,200 yards Grant rushed for in each of the last two seasons remains to be seen.

"When you lose a running back of Ryan's caliber, it's a big loss," Thompson said in a statement. "But this is something we have to deal with and move forward from as a team. We have confidence that our other players will step up and meet the challenge of these losses.""